1. Field of Invention
This invention pertains generally to relays for opening and closing electrical power circuits and, more particularly, to a hybrid power relay having both electromechanical and solid state switching elements.
2. Related Art
The two most common types of switching devices currently available for making and breaking electrical power circuits are electromechanical contactors or relays having mechanical contacts that can be opened or closed by electromagnetic forces, and solid state relays or switches which have no mechanical switching contacts.
The mechanical contacts can generally carry higher electrical currents and thus be used for heavier loads than solid state switching devices, but they are subject to arcing when opened or closed. The solid state devices generally require large heat sinks to protect them from overheating.
Heretofore, there have been some attempts to provide hybrid power relays having both electromechanical contacts and solid state switching, and examples of such devices are found in U.S. Pat. Nos. 2,789,253, 3,237,030, 3,321,668, 3,558,910, 3,639,808, 4,074,333, 5,283,706, 5,528,443, 5,790,354, 6,347,024, and 6,621,668.